This research is designed to answer the question of the possible carcinogenic effects of the consumption of cannabis by smoking. It follows, in detail, the experiments of Wynder and his associates and others in the field of tobacco carcinogenesis. This study is an animal experiment which involves the mechanical production of cannabis smoke in a smoking apparatus and the subsequent condensation of the smoke into tar in a cold trap. These tars are then either subjected to fractionation by chromatographic techniques or used in a crude state. The skin of mice is painted and the subcutaneous tissue of rats is injected with doses which were shown to produce tumors by the experimentors working with tobacco tar. In order to control animal strains and produce a known positive, simultaneous positive controls are run with benzoalphapyrene. Observation and painting continued until tumors occur, at which time the tumors are evaluated by light and electron microscopy. Portions of the tumors are saved for potential viral studies. Pilot study data appended hereto indicates complete ablation of sebaceous glands when tars from cannabis are applied to mice in the method of Suntizeff et al. Such simultaneous sebaceous gland toxicity is highly indicative of potential carcinogenicity. This research is significant in that it will provide answers to the question of possible carcinogenicity of cannabis smoke condensates and may point the way for further studies of the potential carcinogenicity of cannabis smoke for man.